JPH0878015A - Nickel hydrogen battery and hydrogen storage alloy electrode - Google Patents

Abstract

PURPOSE: To provide a nickel hydrogen battery with high performance, capable of suppressing increase in internal pressure caused by hydrogen gas generation, decrease in capacity attendant on repeated charge/discharge cycles, self discharge, and keeping stable performance for a long time by containing an organic sulfur compound having a carbon-sulfur bond in at negative electrode made of a hydrogen storage alloy. CONSTITUTION: A nickel hydrogen battery comprises a positive electrode made mainly of nickel hydroxide, and a negative electrode made mainly of a hydrogen storage alloy capable of electrochemically absorbing/desorbing hydrogen, and contains an organic sulfur compound having a carbon-sulfur bond in the negative electrode. The content of the organic sulfur compound is preferably 0.005-1 pts.wt. based on the 100 pts.wt. of the hydrogen storage allay. As the organic sulfur compound, a material having at least one of single bond C-S, double bond C=S, and multiple bond of carbon and sulfur in part of the molecular structure (example: thiols and sulfides) is used. Preferably, water repellent property is given in at least part of the negative electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-hydrogen battery using nickel hydroxide and a hydrogen storage alloy as electrodes, which suppresses an increase in internal pressure due to hydrogen gas, a decrease in capacity during repeated charging and discharging, and a decrease in voltage due to being left after charging. And the hydrogen storage alloy electrode.

[0002]

2. Description of the Related Art Recent power saving of electronic technology and progress of packaging technology have been remarkable, and have made it possible to make cordless and portable electronic equipment which could not be expected in the past.
Although a sealed nickel-cadmium battery has been used as a power source for the electronic device, the nickel-cadmium battery has drawbacks of environmental pollution and low energy density. Therefore, the development of a nickel-hydrogen battery that is clean and has a relatively high energy density has been urgently promoted.

This nickel-hydrogen battery has a positive electrode containing nickel hydroxide as a main constituent material and hydrogen which is occluded electrochemically.
It is composed of a negative electrode whose main constituent material is a hydrogen storage alloy capable of being released. In this sealed nickel-metal hydride battery, there is a problem that during overcharging, oxygen gas is generated from the positive electrode by the reaction formula shown below, and the internal pressure of the sealed battery rises. The positive _{^{electrode: OH - → 1 / 4O 2}} + 1 / 2H 2 O + e -. _{Negative: M + H 2 O + e} - → MH + OH - ( where, M is a hydrogen absorbing alloy). This problem of internal pressure increase due to oxygen gas has been solved by the positive electrode regulation law adopted in nickel cadmium batteries. The positive electrode regulation method is a method in which the theoretical capacity of the negative electrode is made larger than the theoretical capacity of the positive electrode and the oxygen gas generated is consumed by the solid-gas reaction on the surface of the negative electrode with a margin. That is, the following reactions occur at the negative electrode. Negative electrode: MH + 1 / 4O ₂ → M + 1 / 2H ₂ O.

[0004]

Although the problem of the internal pressure increase due to oxygen gas was solved as described above, hydrogen gas was actually generated in the negative electrode during overcharge, and the internal pressure increase due to this hydrogen gas was solved. There was a problem left. As a remedy, a method has been proposed in which water repellency is imparted to the inside or the surface of the negative electrode to sufficiently secure a solid-gas-liquid three-phase interface and the generated hydrogen is absorbed by the hydrogen storage alloy of the negative electrode. It has not been resolved. It is considered that hydrogen gas is generated in the negative electrode due to the following reaction. ^{_{Anode: H 2 O + e - →}} 1 / 2H 2 + OH -.

The first problem is the internal pressure increase problem caused by the hydrogen gas. Secondly, when the charge / discharge cycle is repeated, the hydrogen storage alloy is dropped or the negative electrode is deteriorated (corroded) to lower the discharge capacity. There was a problem. This has been improved by selecting a binder for the negative electrode constituent material such as hydrogen storage alloy powder, but it cannot be said to be sufficient yet.

The third problem is that the voltage drops if the battery is left unattended after charging. It is considered that this is due to self-discharge, and considerable improvement has been made by studying separators, etc., but further improvement is desired. The present invention is a high-performance nickel that suppresses an increase in internal pressure due to the generation of hydrogen gas, a decrease in capacity during repeated charging / discharging, and a decrease in voltage (self-discharge) after being left after charging, and that provides stable characteristics over a long period of time. It is an object of the present invention to provide a hydrogen storage alloy electrode for a hydrogen battery, the nickel hydrogen battery and the like.

[0007]

According to a first aspect of the present invention, there is provided a positive electrode containing nickel hydroxide as a main constituent material, and a hydrogen storage alloy capable of electrochemically absorbing and desorbing hydrogen as a main constituent material. In a nickel-hydrogen battery consisting of a negative electrode that
The nickel-hydrogen battery is characterized in that the negative electrode contains an organic sulfur compound having a bond of carbon and sulfur.

According to a third aspect of the present invention, in an electrode mainly composed of a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, the organic sulfur compound having a bond of carbon and sulfur in the electrode. The hydrogen storage alloy electrode is characterized by containing:

The invention of claim 1 is a nickel-hydrogen battery,
By containing an organic sulfur compound having a bond of carbon and sulfur in the negative electrode mainly composed of hydrogen storage alloy,
This suppresses an increase in internal pressure due to generation of hydrogen gas, a decrease in capacity during repeated charging / discharging, and a decrease in voltage (self-discharge) after leaving after charging. The invention of claim 3 is a hydrogen storage alloy electrode used in the battery or the like. The above-mentioned organic sulfur compound having a bond of carbon and sulfur is a single bond C—S of carbon and sulfur, a double bond C = S, in a part of the molecular structure.
Alternatively, it is an organic sulfur compound having at least one of multiple bonds. The content of the organic sulfur compound is 0.005 to 1 part by weight with respect to 100 parts by weight of the hydrogen storage alloy. If it is less than 0.005 part by weight, the effect is small, and if it exceeds 1 part by weight, the amount of the hydrogen storage alloy is relatively decreased, the capacity ratio between the negative electrode and the positive electrode is decreased, and the internal pressure is slightly increased. In order to contain the organic sulfur compound in the negative electrode, the organic sulfur compound is added to the hydrogen storage alloy powder and the conductive agent Ni.
A convenient method is to add it to the powder, mix it, and apply this to a porous plate as a paste. However, other methods can be applied arbitrarily.

The organic sulfur compounds are thiols, sulfides, disulfides, polysulfides, thioaldehydes, thioketones, sulfonium compounds, sulfoxides, disulfoxides, sulfones, sulfonic acid derivatives, sulfinic acids, sulfinic acid derivatives. , Sulfenic acids, sulfenic acid derivatives, thio acids, dithio acids,
Sulfur derivatives of carbonic acid, thioamides, carbonyl sulfides,
Thiophosgenes, carbamic acids, sulfur derivatives of urea,
It is selected from the group consisting of thiirane derivatives, sulfilimines, sulfoximines, sulfonyl halides, thiocarbonyl compounds, thiocarboxylic acids, sulfonium salts, oxosulfonium salts, and other organic sulfur compounds. Specifically, n-butylthiol, ethylthioethane, phenyldithiobenzene, trimethylsulfonium = bromide, thiobenzophenone, 2,4-dinitrobenzenesulfenyl chloride, ethanesulfinic acid,
Examples include ethanesulfonic acid, methanesulfonyl chloride, methylsulfinylethane, phenylsulfonylbenzene and the like. These rational formulas or structural formulas are shown in Chemical formula 1.

[0011]

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In the present invention, by imparting water repellency to the negative electrode (the electrode whose main constituent is a hydrogen storage alloy),
The solid-gas-liquid three-phase interface is sufficiently secured, the generated hydrogen is efficiently absorbed by the hydrogen storage alloy, and the decrease of the internal pressure is promoted. Water repellency can be easily imparted by adding a water repellent agent to the hydrogen storage alloy powder. PTFE is used as the water repellent.
Commercially available products such as dispersion (D-1 manufactured by Daikin Industries) and fluororubber latex (GL-252 manufactured by Daikin Industries) can be applied.

[0013]

In the nickel-hydrogen battery of the present invention, since the electrode having the hydrogen storage alloy as the main constituent material is used as the negative electrode and the electrode contains the organic sulfur compound having the bond of carbon and sulfur,
An increase in internal pressure due to hydrogen gas, a decrease in capacity during repeated charging / discharging, and a decrease in voltage after being left after charging are suppressed. Further, the hydrogen storage alloy electrode containing the organic sulfur compound can be used as a negative electrode of a battery to obtain the same effect. By containing an organic sulfur compound in the electrode having the hydrogen storage alloy as a main constituent material, an increase in internal pressure is suppressed because the organic sulfur compound suppresses hydrogen gas generation at the negative electrode during overcharge,
It is considered that this is because it has a function of quickly absorbing the generated hydrogen into the hydrogen storage alloy. It is considered that the reduction in capacity is improved because the organic sulfur compound suppresses deterioration of the hydrogen storage alloy of the negative electrode due to oxidation or hydroxide formation. It is considered that the reduction in voltage is because the organic sulfur compound suppresses oxidation or dehydrogenation of the hydrogen storage alloy of the negative electrode, which causes self-discharge. By imparting water repellency to the electrode containing a hydrogen storage alloy as a main constituent material, a solid-gas-liquid three-phase interface is sufficiently secured, the generated hydrogen is efficiently absorbed by the hydrogen storage alloy, and the internal pressure is reduced.

[0014]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 100 parts by weight of hydrogen storage alloy powder, 0.003 to 1.2 parts by weight of an organic sulfur compound (n-butylthiol, etc.), and 10 parts by weight of Ni powder having an average particle size of about 0.3 μm as a conductive agent were uniformly mixed. Then, 24 parts by weight of a 1 wt% CMC (carboxymethyl cellulose) aqueous solution was added to form a paste. Next, the paste-like material was plated with Ni on both sides to a thickness of 5 μm and the overall thickness was 60 μm, and was made of Fe (aperture ratio 38%).
Was evenly applied to both surfaces of the. Next, this was dried at 80 ° C. and then a roller press was applied to adjust the thickness to about 0.4 mm to manufacture a hydrogen storage alloy electrode. The hydrogen storage alloy powder was prepared as follows. That is, the composition is MmNi _3.23
Co _0.98 Mn _0.29 Al _0.39 hydrogen storage alloy was melt-cast in a vacuum melting furnace under a reduced pressure in an argon atmosphere, and the obtained ingot was subjected to hammer mill crushing and cross beater mill crushing, then an alloy powder of 20 to 60 μm Was classified and used. The Mm is misch metal, La: 26 wt%, Ce: 50 wt
%, Nd: 15 wt%, Pr: 9 wt%. Organic sulfur compounds include n-butylthiol, ethylthioethane, phenyldithiobenzene, trimethylsulfonium bromide, thiobenzophenone, 2,4-dinitrobenzenesulfenyl chloride, ethanesulfinic acid, ethanesulfonic acid, methanesulfonyl chloride. , Methylsulfinylethane, or phenylsulfonylbenzene was used.

(Example 2) 100 parts by weight of hydrogen storage alloy, n-
0.1 parts by weight of butyl thiol, average particle size as conductive agent
10 parts by weight of 0.3 μm Ni powder, as a water repellent agent
Solid content of PTFE dispersion (D-1 from Daikin Industries, Ltd.) or fluororubber latex (GL-252 from Daikin Industries)
1 part by weight of any one of the solid contents was mixed and mixed uniformly, and then 24 parts by weight of a 1 wt% CMC aqueous solution was added to form a paste. The paste-like material was applied on both sides with a thickness of 5 μm of Ni.
It was evenly applied on both sides of a perforated plate made of Fe (pore ratio 38%) which was plated and had a total thickness of 60 μm. After that, keep it at 80 ℃ and dry it.
The hydrogen storage alloy electrode was manufactured by adjusting the above.

(Comparative Example 1) The above hydrogen storage alloy powder 100
10 parts by weight of Ni powder having an average particle size of about 0.3 μm as a conductive agent
Part by weight was mixed, and 24 parts by weight of a 1 wt% CMC aqueous solution was added to this mixed powder to form a paste. The pasty material is plated on both sides with a thickness of 5 μm and the total thickness is 60 μm.
m Fe perforated plate (opening rate 38%) was evenly applied to both sides. Then, it was kept at 80 ° C. and dried, and was roller pressed to adjust the thickness to about 0.4 mm to manufacture a hydrogen storage alloy electrode.

Comparative Example 2 Hydrogen absorption was carried out by the same method as in Comparative Example 1 except that 0.1 part by weight of dimethyl sulfate (organic sulfur compound having no carbon-sulfur bond) was added to the mixed powder in Comparative Example 1. Alloy electrodes were manufactured. In addition, the first embodiment
All the electrodes of Comparative Example 2 had a porosity of about 20% and a hydrogen storage alloy packing density of about 4.6 g / cm ³ .

A sealed nickel-hydrogen battery (AA size of 1100 mAh) having the structure shown in FIG. 1 was assembled using the thus obtained hydrogen storage alloy electrodes by the following procedure. A negative electrode 1 obtained by cutting each hydrogen storage alloy electrode into a predetermined shape, and a nickel positive electrode 2 obtained by filling a commercially available foamed nickel substrate with a paste-like material containing nickel hydroxide as a main constituent material via a nylon non-woven fabric separator 3. Spirally,
This was inserted into a battery case 4 which also serves as a negative electrode terminal. After that, the required amount of alkaline electrolyte was injected. Here, the theoretical capacity of the negative electrode was about 1.6 times that of the positive electrode. The safety valve 6 formed inside the positive electrode cap 5 was adjusted so that the valve was activated when the pressure reached about 3.0 MPa. 1mm diameter at the bottom of battery case 4
A hole was drilled to attach a pressure sensor for measuring internal pressure. In the figure, 7 is a sealing plate and 8 is an insulating gasket.

A battery test was carried out on each of the batteries thus assembled under the following conditions. Battery internal pressure test: Charged up to 450% of the positive electrode capacity at a charging current of 1 CmA at 20 ° C, and measured the internal battery pressure at that time. Charge / discharge cycle test: 150% of the positive electrode capacity is charged at a charge current of 1 CmA at 20 ° C and 1 V at a discharge current of 1 CmA.
The discharge capacity retention rate of the charge / discharge cycle test was observed when the cycle was repeated 500 times and the cycle was repeated 500 times. The discharge capacity retention rate was expressed as a percentage of the capacity in each cycle with respect to the initial capacity. The initial capacity was between 1170 and 1200 mAh for all batteries. Voltage drop test: After charging 150% of the positive electrode capacity under the conditions of a temperature of 20 ° C and a charging current of 1 CmA, leave it at a temperature of 80 ° C for 100 days and measure the time required for the OPEN voltage of the battery to drop to 1V. did. The results are shown in Table 1 and FIG. FIG. 2 is a relationship diagram between the number of cycles and the capacity retention rate in the charge / discharge cycle test.

[0020]

[Table 1]

As is clear from Table 1 and FIG. 2, the products of the present invention (Nos. 1 to 17) all have an internal pressure of 0.1 to 0.7 MPa.
And the charge / discharge capacity retention rate after 500 cycles is 94.5%.
Above all, the voltage drop required time was 210 hours or more, and the self-discharge suppression effect was large, showing superior characteristics to the comparative product No. 19 (conventional product). The battery of the present invention has a charge / discharge retention rate after 500 cycles of 8% or more compared with the conventional product, and has a capacity of about 10%.
It was as high as 0 mAh or more. In Nos. 16 and 17, since the water repellent was added, the solid-gas-liquid three-phase interface was sufficiently secured, and the internal pressure was remarkably reduced. Incidentally, No. 4 had a small amount of organic sulfur compounds, and thus all properties were slightly deteriorated. No. 5 had a large internal pressure because it contained many organic sulfur compounds. On the other hand, Comparative Example No. 18 contained an organic sulfur compound having no bond between carbon and sulfur, and therefore the improvement in properties was not observed so much.

[0022]

According to the nickel-hydrogen battery of the present invention, an electrode containing a hydrogen storage alloy as a main constituent material is used as a negative electrode,
Since it contains an organic sulfur compound that has a bond of carbon and sulfur, the internal pressure rises due to hydrogen gas, the capacity decreases during repeated charge and discharge, and the voltage decreases after charging (self-discharge).
Is suppressed. Further, the hydrogen storage alloy electrode containing the organic sulfur compound can be used as a negative electrode of a battery to obtain the same effect.

[Brief description of drawings]

FIG. 1 is an explanatory view of assembly of a nickel hydrogen battery.

FIG. 2 is a relationship diagram between the number of cycles and a capacity retention rate in a charge / discharge cycle test.

[Explanation of symbols]

 1 ... Negative electrode 2 ... Positive electrode 3 ... Separator 4 ... Battery case 5 ... Positive electrode cap 6 ... Safety valve 7 ... Sealing plate 8 ... Insulation gasket

Claims (4)

[Claims] 1. A nickel-hydrogen battery comprising a positive electrode containing nickel hydroxide as a main constituent material, and a negative electrode containing a hydrogen storage alloy capable of electrochemically absorbing and desorbing hydrogen as a main constituent material. A nickel-hydrogen battery, wherein the negative electrode contains an organic sulfur compound having a bond of carbon and sulfur. 2. The nickel-hydrogen battery according to claim 1, wherein at least a part of the negative electrode is provided with water repellency. 3. An electrode mainly comprising a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, wherein the electrode contains an organic sulfur compound having a bond of carbon and sulfur. A hydrogen storage alloy electrode. 4. The hydrogen storage alloy electrode according to claim 3, wherein water repellency is imparted to at least a part of the electrode.